Hello, you are mixing keywords and value.
Please I encourage you to read again (even if it is one of the hardest part to understand in terms of configuration) in the fine manual, this section again.
Especially the diverse examples
Normally what you would like to achieve can be written
Run = Full 1,16 at 21:00
Run = Incremental 2-15,17-31 at 21:00
But you want maybe to play with the modulo ;-)